a
The amount carried by pipeline is based
on ton-miles of crude and petroleum products transported through federally
regulated pipelines (84%), plus estimated ton-miles of crude and petroleum
products transported through nonfederally regulated pipelines (16%).

b The amount carried by motor carriers is
estimated.

c
Reflects the entrance between 1975 and
1980 of the Alaska pipeline, moving crude petroleum for water transportation
to U.S. refineries.